During oil or gas well operation, it is common to perforate the well casing in order to create a flow path for the oil and/or gas to flow into the well. This may be done by introducing downhole tools into the well casing typically using a single-conductor, steel armoured electrical cable, a ‘logging’ or ‘wireline’ cable. Such downhole tools may include perforating guns which fire explosive charges through the well casing. It is essential that the explosive charges are not detonated accidentally due to the potential damage they may cause and the risk to life they pose.
As the number of devices (‘guns’) in a downhole perforating string increases, so does the number of switch devices used to safely route power to the detonator when required. The current and voltage required to power the tool string also increases as there is a voltage drop across each switch. Explosive detonators have a certain minimum voltage required to initiate detonation. For safety reasons, it is important that the total power sent to a tool string comprising switch devices and detonator devices during normal, non-detonation events, is lower than the power required to initiate a detonator. Typically this limits the number of detonation devices that can be deployed in a tool string to 15 or fewer.
The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved detonation device.